Disposable cartridge for producing gas-enriched fluids

ABSTRACT

A device generates a gas-enriched physiologic fluid and combines it with a bodily fluid to create a gas-enriched bodily fluid. The device may take the form of a disposable cartridge. The cartridge may include a fluid supply chamber for delivering physiologic fluid under pressure to an atomizer. The atomizer delivers fluid droplets into a gas-pressurized atomization chamber to enrich the physiologic fluid with the gas. The gas-enriched physiologic fluid is delivered to a mixing chamber in the cartridge where the gas-enriched physiologic fluid is mixed with a bodily fluid, such as blood, to create a gas-enriched bodily fluid.

Related Applications

This patent application is a divisional of U.S. patent application Ser.No. 09/813,062, filed on Mar. 20, 2001 now U.S. Pat. No. 6,613,280.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the gas enrichment of a fluidand, more particularly, to a disposable cartridge for producing agas-enriched fluid.

2. Background of the Related Art

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present invention thatare described and/or claimed below. This discussion is believed to behelpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentinvention. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

Gas-enriched fluids are used in a wide variety of medical, commercial,and industrial applications. Depending upon the application, aparticular type of fluid is enriched with a particular type of gas toproduce a gas-enriched fluid having properties that are superior to theproperties of either the gas or fluid alone for the given application.The techniques for delivering gas-enriched fluids also varydramatically, again depending upon the particular type of applicationfor which the gas-enriched fluid is to be used.

Many commercial and industrial applications exist. As one example,beverages may be purified with the addition of oxygen and carbonatedwith the addition of carbon dioxide. As another example, thepurification of wastewater is enhanced by the addition of oxygen tofacilitate aerobic biological degradation. As yet another example, infire extinguishers, an inert gas, such as nitrogen, carbon dioxide, orargon, may be dissolved in water or another suitable fluid to produce agas-enriched fluid that expands on impact to extinguish a fire.

While the commercial and industrial applications of gas-enriched fluidsare relatively well known, gas-enriched fluids are continuing to makeinroads in the healthcare industry. Oxygen therapies, for instance, arebecoming more popular in many areas. A broad assortment of treatmentsinvolving oxygen, ozone, H₂O₂, and other active oxygen supplements hasgained practitioners among virtually all medical specialties. Oxygentherapies have been utilized in the treatment of various diseases,including cancer, AIDS, and Alzheimer's. Ozone therapy, for instance,has been used to treat several million people in Europe for a variety ofmedical conditions including excema, gangrene, cancer, stroke,hepatitis, herpes, and AIDS. Such ozone therapies have become popular inEurope because they tend to accelerate the oxygen metabolism andstimulate the release of oxygen in the bloodstream.

Oxygen is a crucial nutrient for human cells. It produces energy forhealthy cell activity and acts directly against foreign toxins in thebody. Indeed, cell damage may result from oxygen depravation for evenbrief periods of time, and such cell damage can lead to organdysfunction or failure. For example, heart attack and stroke victimsexperience blood flow obstructions or divergence that prevent oxygen inthe blood from being delivered to the cells of vital tissues. Withoutoxygen, these tissues progressively deteriorate and, in severe cases,death may result from complete organ failure. However, even less severecases can involve costly hospitalization, specialized treatments, andlengthy rehabilitation.

Blood oxygen levels may be described in terms of the concentration ofoxygen that can be achieved in a saturated solution at a given partialpressure of oxygen (pO₂). Typically, for arterial blood, normal oxygenlevels, i.e., normoxia or normoxemia, range from 90 to 110 mmHg.Hypoxemic blood, i.e., hypoxemia, is arterial blood with a pO₂ less than90 mmHg. Hyperoxemic blood, i.e., hyperoxemia or hyperoxia, is arterialblood with a pO₂ greater than 400 mmHg, but less than 760 mmHg.Hyperbaric blood is arterial blood with a pO₂ greater than 760 mmHg.Venous blood, on the other hand, typically has a pO₂ level less than 90mmHg. In the average adult, for example, normal venous blood oxygenlevels range generally from 40 mmHg to 70 mmHg.

Blood oxygen levels also may be described in terms of hemoglobinsaturation levels. For normal arterial blood, hemoglobin saturation isabout 97% and varies only as pO₂ levels increase. For normal venousblood, hemoglobin saturation is about 75%. Indeed, hemoglobin isnormally the primary oxygen carrying component in blood. However, oxygentransfer takes place from the hemoglobin, through the blood plasma, andinto the body's tissues. Therefore, the plasma is capable of carrying asubstantial quantity of oxygen, although it does not normally do so.Thus, techniques for increasing the oxygen levels in blood primarilyenhance the oxygen levels of the plasma, not the hemoglobin.

The techniques for increasing the oxygen level in blood are not unknown.For example, naval and recreational divers are familiar with hyperbaricchamber treatments used to combat the bends, although hyperbaricmedicine is relatively uncommon for most people. Since hemoglobin isrelatively saturated with oxygen, hyperbaric chamber treatments attemptto oxygenate the plasma. Such hyperoxygenation is believed to invigoratethe body's white blood cells, which are the cells that fight infection.Hyperbaric oxygen treatments may also be provided to patients sufferingfrom radiation injuries. Radiation injuries usually occur in connectionwith treatments for cancer, where the radiation is used to kill thetumor. Unfortunately, at present, radiation treatments also injuresurrounding healthy tissue as well. The body keeps itself healthy bymaintaining a constant flow of oxygen between cells, but radiationtreatments can interrupt this flow of oxygen. Accordingly,hyperoxygenation can stimulate the growth of new cells, thus allowingthe body to heal itself.

Radiation treatments are not the only type of medical therapy that candeprive cells from oxygen. In patients who suffer from acute myocardialinfarction, for example, if the myocardium is deprived of adequatelevels of oxygenated blood for a prolonged period of time, irreversibledamage to the heart can result. Where the infarction is manifested in aheart attack, the coronary arteries fail to provide adequate blood flowto the heart muscle. The treatment for acute myocardial infarction ormyocardial ischemia often involves performing angioplasty or stenting ofvessels to compress, ablate, or otherwise treat the occlusions withinthe vessel walls. In an angioplasty procedure, for example, a balloon isplaced into the vessel and inflated for a short period of time toincrease the size of the interior of the vessel. When the balloon isdeflated, the interior of the vessel will, hopefully, retain most or allof this increase in size to allow increased blood flow.

However, even with the successful treatment of occluded vessels, a riskof tissue injury may still exist. During percutaneous transluminalcoronary angioplasty (PTCA), the balloon inflation time is limited bythe patient's tolerance to ischemia caused by the temporary blockage ofblood flow through the vessel during balloon inflation. Ischemia is acondition in which the need for oxygen exceeds the supply of oxygen, andthe condition may lead to cellular damage or necrosis. Reperfusioninjury may also result, for example, due to slow coronary reflow or noreflow following angioplasty. Furthermore, for some patients,angioplasty procedures are not an attractive option for the treatment ofvessel blockages. Such patients are typically at increased risk ofischemia for reasons such as poor left ventricular function, lesion typeand location, or the amount of myocardium at risk. Treatment options forsuch patients typically include more invasive procedures, such ascoronary bypass surgery.

To reduce the risk of tissue injury that may be associated withtreatments of acute myocardial infarction and myocardial ischemia, it isusually desirable to deliver oxygenated blood or oxygen-enriched fluidsto the tissues at risk. Tissue injury is minimized or prevented by thediffusion of the dissolved oxygen from the blood to the tissue. Thus, insome cases, the treatment of acute myocardial infarction and myocardialischemia includes perfusion of oxygenated blood or oxygen-enrichedfluids. The term “perfusion” is derived from the French verb “perfuse”meaning “to pour over or through.” In this context, however, perfusionrefers to various techniques in which at least a portion of thepatient's blood is diverted into an extracorporeal circulation circuit,i.e., a circuit which provides blood circulation outside of thepatient's body. Typically, the extracorporeal circuit includes anartificial organ that replaces the function of an internal organ priorto delivering the blood back to the patient. Presently, there are manyartificial organs that can be placed in an extracorporeal circuit tosubstitute for a patient's organs. The list of artificial organsincludes artificial hearts (blood pumps), artificial lungs(oxygenators), artificial kidneys (hemodialysis), and artificial livers.

During PTCA, for example, the tolerable balloon inflation time may beincreased by the concurrent introduction of oxygenated blood into thepatient's coronary artery. Increased blood oxygen levels also may causethe hypercontractility in the normally perfused left ventricular cardiactissue to increase blood flow further through the treated coronaryvessels. The infusion of oxygenated blood or oxygen-enriched fluids alsomay be continued following the completion of PTCA or other procedures,such as surgery, to accelerate the reversal of ischemia and tofacilitate recovery of myocardial function.

Conventional methods for the delivery of oxygenated blood oroxygen-enriched fluids to tissues involve the use of blood oxygenators.Such procedures generally involve withdrawing blood from a patient,circulating the blood through an oxygenator to increase blood oxygenconcentration, and then delivering the blood back to the patient. Thereare drawbacks, however, to the use of conventional oxygenators in anextracorporeal circuit. Such systems typically are costly, complex, anddifficult to operate. Often, a qualified perfusionist is required toprepare and monitor the system. A perfusionist is a skilled healthprofessional specifically trained and educated to operate as a member ofa surgical team responsible for the selection, setup, and operation ofan extracorporeal circulation circuit. The perfusionist is responsiblefor operating the machine during surgery, monitoring the alteredcirculatory process closely, taking appropriate corrective action whenabnormal situations arise, and keeping both the surgeon andanesthesiologist fully informed. In addition to the operation of theextracorporeal circuit during surgery, perfusionists often function insupportive roles for other medical specialties to assist in theconservation of blood and blood products during surgery and to providelong-term support for patient's circulation outside of the operatingroom environment. Because there are currently no techniques available tooperate and monitor an extracorporeal circuit automatically, thepresence of a qualified perfusionist, and the cost associated therewith,is typically required.

Conventional extracorporeal circuits also exhibit other drawbacks. Forexample, extracorporeal circuits typically have a relatively largepriming volume. The priming volume is typically the volume of bloodcontained within the extracorporeal circuit, i.e., the total volume ofblood that is outside of the patient's body at any given time. Forexample, it is not uncommon for the extracorporeal circuit to hold oneto two liters of blood for a typical adult patient. Such large primingvolumes are undesirable for many reasons. For example, in some cases ablood transfusion may be necessary to compensate for the bloodtemporarily lost to the extracorporeal circuit because of its largepriming volume. Also, heaters often must be used to maintain thetemperature of the blood at an acceptable level as it travels throughthe extracorporeal circuit. Further, conventional extracorporealcircuits are relatively difficult to turn on and off. For instance, ifthe extracorporeal circuit is turned off, large stagnant pools of bloodin the circuit might coagulate.

In addition to the drawbacks mentioned above, in extracorporeal circuitsthat include conventional blood oxygenators, there is a relatively highrisk of inflammatory cell reaction and blood coagulation due to therelatively slow blood flow rates and large blood contact surface area ofthe oxygenators. For example, a blood contact surface area of about oneto two square meters and velocity flows of about 3 centimeters/secondare not uncommon with conventional oxygenator systems. Thus, relativelyaggressive anti-coagulation therapy, such as heparinization, is usuallyrequired as an adjunct to using the oxygenator.

Finally, perhaps one of the greatest disadvantages to using conventionalblood oxygenation systems relates to the maximum partial pressure ofoxygen (pO₂ ) that can be imparted to the blood. Conventional bloodoxygenation systems can prepare oxygen-enriched blood having a partialpressure of oxygen of about 500 mmHg. Thus, blood having pO₂ levels nearor above 760 mmHg, i.e., hyperbaric blood, cannot be achieved withconventional oxygenators.

It is desirable to deliver gas-enriched fluid to a patient in a mannerwhich prevents or minimizes bubble nucleation and formation uponinfusion into the patient. The maximum concentration of gas achievablein a liquid is ordinarily governed by Henry's Law. At ambienttemperature, the relatively low solubility of many gases, such as oxygenor nitrogen, within a liquid, such as water, produces a lowconcentration of the gas in the liquid; However, such low concentrationsare typically not suitable for treating patients as discussed above.Rather, it is advantageous to use a gas concentration within a liquidthat greatly exceeds its solubility at ambient temperature. Compressionof a gas and liquid mixture at a high pressure can be used to achieve ahigh dissolved gas concentration according to Henry's Law, butdisturbance of a gas-saturated or a gas-supersaturated liquid byattempts to inject it into an environment at ambient pressure from ahigh pressure reservoir ordinarily results in cavitation inception at ornear the exit port. The rapid evolution of bubbles produced at the exitport vents much of the gas from the liquid, so that a high degree ofgas-supersaturation no longer exists in the liquid at ambient pressureoutside the high-pressure vessel. In addition, the presence of bubblesin the effluent generates turbulence and impedes the flow of theeffluent beyond the exit port. Furthermore, the coalescence of gasbubbles in blood vessels may tend to occlude the vessels and result in agaseous local embolism that causes a decrease in local circulation,arterial hypoxemia, and systemic hypoxia.

In gas-enriched fluid therapies, such as oxygen therapies involving theuse of hyperoxic or hyperbaric blood, delivery techniques are utilizedto prevent or minimize the formation of cavitation nuclei so thatclinically significant bubbles do not form within a patient's bloodvessels. However, it should be understood that any bubbles that areproduced tend to be very small in size, so that a perfusionist wouldtypically have difficulty detecting bubble formation without theassistance of a bubble detection device. Unfortunately, known bubbledetectors are ineffective for detecting bubbles in an extracorporealcircuit for the preparation and delivery of hyperoxic or hyperbaricblood. This problem results from the fact that the size and velocity ofsome bubbles are beyond the resolution of known bubble detectors.Therefore, micro bubbles (bubbles with diameters of about 50 micrometersto about 1000 micrometers) and some macro bubbles (bubbles withdiameters greater than 1000 micrometers) may escape detection.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings in which:

FIG. 1 illustrates a perspective view of an exemplary system forproducing gas-enriched fluid;

FIG. 2 illustrates a block diagram of the system of FIG. 1;

FIG. 3 illustrates a block diagram of the host/user interface used inthe system of FIG. 1;

FIG. 4 illustrates an exemplary display;

FIG. 5 illustrates a block diagram of a blood pump system used in thesystem of FIG. 1;

FIG. 6 illustrates an interlock system used in the system of FIG. 1;

FIG. 7 illustrates a top view of an oxygenation device used in thesystem of FIG. 1;

FIG. 8 illustrates a cross-sectional view taken along line 8-8 in FIG.7;

FIG. 9 illustrates a bottom view of the oxygenation device used in thesystem of FIG. 1;

FIG. 10 illustrates a detailed view of a check valve illustrated in FIG.8;

FIG. 11 illustrates a detailed view of a piston assembly illustrated inFIG. 8;

FIG. 12 illustrates a cross-sectional view taken along line 12-12 ofFIG. 8;

FIG. 13 illustrates a detailed view of a valve assembly illustrated inFIG. 8;

FIG. 14 illustrates a cross-sectional view of the valve assembly takenalong line 14-14 in FIG. 13;

FIG. 15 illustrates a detailed view of a capillary tube illustrated inFIG. 8;

FIG. 16 illustrates a detailed view of a vent valve illustrated in FIG.8;

FIG. 17 illustrates an exploded view of the cartridge and cartridgeenclosure;

FIG. 18 illustrates a front view of the cartridge receptacle of thecartridge enclosure illustrated in FIG. 1;

FIG. 19 illustrates a cross-sectional view of the cartridge enclosuretaken along line 19-19 in FIG. 18;

FIG. 20 illustrates the front view of a door latch on the door of thecartridge enclosure;

FIG. 21 illustrates a cross-sectional view of the door latch taken alongline 21-21 in FIG. 20;

FIG. 22 illustrates another cross-sectional view of the door latch;

FIG. 23 illustrates a detailed view of the door latch of FIG. 19;

FIG. 24 illustrates a cross-sectional view of the door latch including ablocking mechanism;

FIG. 25 illustrates a cross-sectional view of the locking mechanism ofFIG. 24 as the latch is being closed;

FIG. 26 illustrates a cross-sectional view of the locking mechanismafter the latch has been closed;

FIG. 27 illustrates a bottom view of the cartridge enclosure;

FIG. 28 illustrates a cross-sectional view taken along line 28-28 inFIG. 27 of a valve actuation device in an extended position;

FIG. 29 illustrates a cross-sectional view taken along line 28-28 inFIG. 27 of a valve actuation device in a retracted position;

FIG. 30 illustrates a top-view of the cartridge enclosure;

FIG. 31 illustrates a cross-sectional view taken along line 31-31 ofFIG. 30 of a valve actuation device in its extended position;

FIG. 32 illustrates a cross-sectional view taken along line 31-31 ofFIG. 30 of a valve actuation device in its retracted position;

FIG. 33 illustrates a cross-sectional view of the cartridge enclosuretaken along line 33-33 in FIG. 18;

FIG. 34 illustrates a detailed view of an ultrasonic sensor illustratedin FIG. 33;

FIG. 35 illustrates a detailed view of an ultrasonic sensor illustratedin FIG. 33;

FIG. 36 illustrates a top view of the cartridge enclosure including gasconnections;

FIG. 37 illustrates a cross-sectional view taken along line 37-37 inFIG. 36;

FIG. 38 illustrates a detailed view of the cross-sectional view of FIG.37 of a gas connection in an unseated position;

FIG. 39 illustrates a detailed view of the cross-sectional view of FIG.37 of a gas connection in a seated position;

FIG. 40 illustrates a partial cross-sectional view of a drive mechanism;

FIGS. 41A and B illustrate an exploded view of the drive mechanismillustrated in FIG. 40;

FIG. 42 illustrates a cross-sectional view taken along line 42-42 inFIG. 40;

FIG. 43 illustrates a detailed view of the load cell illustrated in FIG.42;

FIG. 44 illustrates an exploded view of a sensor assembly of the drivemechanism;

FIG. 45 illustrates a top partial cross-sectional view of the driveassembly;

FIG. 46 illustrates a cross-sectional view taken along line 46-46 ofFIG. 45;

FIG. 47 illustrates a detailed view of a portion of the sensor assemblyillustrated in FIG. 46;

FIG. 48 illustrates an exemplary sensor for use in the sensor assemblyillustrated in FIG. 44;

FIG. 49 illustrates a state diagram depicting the basic operation of thesystem illustrated in FIG. 1;

FIG. 50 illustrates a block diagram of a system controller;

FIG. 51 illustrates a block diagram of a bubble detector;

FIG. 52 illustrates an exemplary signal transmitted by the bubbledetector;

FIG. 53 illustrates an exemplary signal received by the bubble detector;

FIG. 54 illustrates a bubble sensor coupled to the return tube;

FIG. 55 illustrates a cross-sectional view of the return tube of FIG.54;

FIG. 56 illustrates a schematic diagram of a system used to evaluatebubble detectors, such as the bubble detector of the present system;

FIG. 57 illustrates an elevated side view of an exemplary capillarytube;

FIG. 58 illustrates a side view of the capillary tube of FIG. 57positioned within a connecting device incident to a material flow;

FIG. 59 illustrates a schematic diagram of an alternative system used toevaluate bubble detectors, where the system includes a pulse dampener;

FIG. 60 illustrates a detailed view of an exemplary pulse dampener, and

FIG. 61 illustrates the output of a digital signal processor indicatingthe diameters of bubbles detected by the bubble detector.

DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments of the present invention will bedescribed below. In an effort to provide a concise description of theseembodiments, not all features of an actual implementation are describedin the specification. It should be appreciated that in the developmentof any such actual implementation, as in any engineering or designproject, numerous implementation-specific decisions must be made toachieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

System Overview

Turning now to the drawings, and referring initially to FIG. 1, a systemfor preparing and delivering gas-enriched fluid is illustrated anddesignated by a reference numeral 10. Although the system 10 may be usedto prepare a number of different types of gas-enriched fluids, in thisparticular example, the system 10 prepares oxygen-enriched blood. Aswill be described in detail herein, the system 10 is adapted to withdrawblood from a patient, combine the blood with a oxygen-supersaturatedphysiologic fluid, and deliver the oxygen-enriched blood back to thepatient.

Because the system 10 may be used during surgical procedures, it istypically sized to be placed within a normal operating room environment.Although the system 10 may be configured as a stationary device or afixture within an operating room, it is often desirable for varioussurgical devices to be mobile. Accordingly, in this example, the system10 is illustrated as being coupled to a rolling base 12 via a pedestal14. Although some of the electrical and/or mechanical components of thesystem 10 may be housed in the base 12 or the pedestal 14, thesecomponents will more typically be placed within a housing 16. Tofacilitate positioning of the system 10, a handle 18 may be coupled tothe housing 16 for directing movement of the system 10, and a pedal 20may be coupled to the base 12 for raising and lowering the housing 16 onthe pedestal 14 (via a rack and pinion mechanism which is not shown, forinstance).

The housing 16 may include a cover, such as a hinged door 22, forprotecting certain components of the system 10 that are positioned inlocations external to the housing 16. Components that are typicallylocated on the exterior of the housing 16 may include a blood pump 24, acartridge enclosure 26, as well as various control devices 28.Additional external items may include a user interface panel 30 and adisplay 32.

Referring now to FIG. 2, a block diagram representing various componentsof the system 10 is illustrated. An appropriate draw tube 34, such as anintroducer sheath, is inserted into an appropriate blood vessel 36 of apatient 38. Blood is drawn from the patient 38 through the draw tube 34using the blood pump system 24. Specifically, the blood pump system 24includes a pump 40, such as a peristaltic pump. As the peristaltic pump40 mechanically produces waves of contraction along the flexible tube34, fluid within the tube 34 is pumped in the direction of the arrow 42.As will be discussed in detail below, the blood pump system 24 includesa flow meter 46 that receives feedback from a flow probe 48. The flowprobe 48 is coupled to the patient's return tube 50. With this feedback,the blood pump system 24 can operate as an automatic extracorporealcircuit that can adjust the r.p.m. of the peristaltic pump 40 tomaintain the desired blood flow.

The draw tube 34 and/or the return tube 50 may be sub-selectivecatheters. The construction of the return tube 50 may be of particularimportance in light of the fact that the gas-enriched bodily fluid maybe gas-saturated or gas-supersaturated over at least a portion of thelength of the return tube 50. Therefore, the return tube 50, inparticular, is typically designed to reduce or eliminate the creation ofcavitation nuclei which may cause a portion of the gas to come out ofsolution. For example, the length-to-internal diameter ratio of thecatheter may be selected to create a relatively low pressure drop fromthe oxygenation device 54 to the patient 38. Typically, the catheter issized to fit within a 6 french guide catheter. Materials such aspolyethylene or PEBAX (polyetheramide), for example, may be used in theconstruction of the catheter. Also, the lumen of the catheter should berelatively free of transitions that may cause the creation of cavitationnuclei. For example, a smooth lumen having no fused polymer transitionstypically works well.

The blood is pumped through the draw tube 34 in the direction of thearrow 52 into an oxygenation device 54. Although various different typesof oxygenation devices may be suitable for oxygenating the patient'sblood prior to its return, the oxygenation device 54 in the system 10advantageously prepares an oxygen-supersaturated physiologic fluid andcombines it with the blood to enrich the blood with oxygen. Also, theoxygenation device 54 is advantageously sterile, removable, anddisposable, so that after the procedure on the patient 38 has beencompleted, the oxygenation device 54 may be removed and replaced withanother oxygenation device 54 for the next patient.

Advantages of the oxygenation device 54 will be described in greatdetail below. However, for the purposes of the discussion of FIG. 2, itis sufficient at this point to understand that the physiologic fluid,such as saline, is delivered from a suitable supply 56, such as an IVbag, to a first chamber 58 of the oxygenation device 54 under thecontrol of a system controller 55. A suitable gas, such as oxygen, isdelivered from a supply 60, such as a tank, to a second chamber 62 ofthe oxygenation device 54. Generally speaking, the physiologic fluidfrom the first chamber 58 is pumped into the second chamber 62 andatomized to create a oxygen-supersaturated physiologic solution. Thisoxygen-supersaturated physiologic solution is then delivered into athird chamber 64 of the oxygenation device 54 along with the blood fromthe patient 38. As the patient's blood mixes with theoxygen-supersaturated physiologic solution, oxygen-enriched blood iscreated. This oxygen-enriched blood is taken from the third chamber 64of the oxygenation device 54 by the return tube 50.

A host/user interface 66 of the system 10 monitors both the pressure onthe draw tube 34 via a draw pressure sensor 68 and the pressure on thereturn tube 50 via a return pressure sensor 70. As illustrated in FIG.6, the ends of the draw tube 34 and the return tube 50 that couple tothe oxygenation device 54 are embodied in a Y-connector 71 in thisexample. The Y-connector 71 includes the draw pressure sensor 68 and thereturn pressure sensor 70, which are operatively coupled to thehost/user interface 66 via an electrical connector 73. The host/userinterface 66 may deliver these pressure readings to the display 32 sothat a user can monitor the pressures and adjust them if desired. Thehost/user interface 66 also receives a signal from a level sensor 72that monitors the level of fluid within the mixing chamber 64 of theoxygenation device 54 to ensure that the oxygen-supersaturatedphysiological solution is mixing with the patient's blood with little orno bubble formation.

The system 10 further advantageously includes a suitable bubble detector74. The bubble detector 74 includes a suitable bubble sensor 76positioned at the return tube 50 to detect bubbles as they pass throughthe return tube 50 to the patient 38. Again, as discussed in greaterdetail below, the bubble detector 74 receives the signals from thebubble sensor 76 and processes information regarding the nature of anybubbles that may be traveling in the oxygen-enriched blood going back tothe patient 38. In this embodiment, the bubble detector 74 provides thisinformation to the host/user interface 66 so that information regardingbubbles in the effluent may be provided to the user via the display 32.The bubble detector 74 may also control or shut down the system 10 incertain circumstances as discussed in detail below.

The system 10 also includes an interlock system 44. The interlock system44 communicates with many of the components of the system 10 for variousreasons. The interlock system 44 monitors the various components toensure that the system 10 is operating within certain prescribed bounds.For example, the interlock system 44 receives information regarding drawand return pressures from the pressure sensors 68 and 70, informationregarding fluid level in the mixing chamber 64 from the level sensor 72,and information regarding the number and/or size of bubbles from thebubble detector 74, as well as other information regarding the operatingstates of the various components. Based on this information, theinterlock system 44 can shut down the system 10 should it begin tooperate outside of the prescribed bounds. For example, the interlocksystem 44 can engage clamps 78 and 80 on the draw tube 34 and the returntube 50, respectively, as well as disable the blood pump system 24 andthe system controller 55 that controls the oxygenation device 54. Whilethe interlock system 44 typically operates in this automatic fashion, asafety switch 82 may be provided so that a user can initiate a shutdownof the system 10 in the same fashion even if the system 10 is operatingwithin its prescribed bounds.

The system 10 has a low priming volume relative to conventionalextracorporeal circuits, typically in the range of 25 to 100milliliters. Thus, a heater typically is not used with the system 10.However, if it is desirable to control the temperature of the incomingblood in the draw tube 34 or the outgoing gas-enriched blood in thereturn tube 50, an appropriate device, such as a heat exchanger, may beoperatively coupled to one or both of the tubes 34 and 50. Indeed, notonly may the heat exchanger (not shown) be used to warm the fluid as ittravels through the system 10, it may also be used to cool the fluid. Itmay be desirable to cool the fluid because moderate hypothermia, around30° C. to 34° C. has been shown to slow ischemic injury in myocardialinfarction, for example.

Host/User Interface

The various details of the system 10 described above with reference toFIGS. 1 and 2 will be described with reference to the remaining FIGS.Turning now to FIG. 3, an exemplary embodiment of the host/userinterface 66 is illustrated. The host/user interface 66 includes a userinterface 84 and a host interface 85. The user interface 84 may includea user input and display device, such as a touch screen display 86. Asillustrated in FIG. 4, the touch screen display 86 may include “buttons”87 that initiate certain operations when a user touches them. The touchscreen display 86 may also include information such as alarms/messages88, status indicators 89, blood flow information 90, and bubble count91.

The user inputs are handled by a touch screen driver 92, and thedisplayed information is handled by a display driver 93. The touchscreen driver 92 transmits user inputs to an interface, such as anRS-232 interface 94. The RS-232 interface 94 may communicate these userinputs to other portions of the system 10, such as the system controller55, the interlock system 44, the blood pump system 24, and the bubbledetector 74. The display driver 93 communicates with a displaycontroller 95, which is also coupled to the RS-232 interface 94 via abus 96. The display controller 95 receives updated information from thevarious other portions of the system 10, and it uses this information toupdate the display 86.

The host interface 85 may also include various other capabilities. Forexample, the host interface 85 may include a sound card 97 to drivespeakers 98 on the user interface 84. In addition, a network adapter 99may allow the host interface 85 to communicate with an external network,such as a LAN in the hospital or a remote network for providing updatesfor the system 10, e.g., the Internet. Finally, the host interface 85may include an analog and/or digital I/O device 101, which in thisexample transmits and receives certain signals such as an enable signal,a “request to stop” signal, a draw pressure signal, and a returnpressure signal.

Blood Pump System and Interlock System

Many of the components described below, while particularly useful in theexemplary system 10, may be quite useful in other types of systems aswell. For example, the blood pump system 24 described in detail withreference to FIG. 5 may be used not only in the context of the system10, but also in other types of perfusion systems, such as conventionalheart-lung machines and other types of other extracorporeal circuits. Aspreviously discussed, the blood pump system 24 utilizes a suitable pump40, such as a peristaltic pump, to draw blood from the patient 38through a draw tube 34. The blood pump system 24 further includes a flowmeter 46, such as a transonic flow meter, which communicates with a flowtransducer 48 via lines 100 and 102. The feedback from the transducer 48enables the blood pump system 24 to maintain the desired flow rate. Thedesired flow rate may be entered by a user, such as perfusionist or anurse, via the control panel 30. In this example, the control panel 30includes an indication of the current blood flow rate in milliliters perminute, as well as an “up” button 104 and a “down” button 106 thatpermit a user to adjust the blood flow rate upwardly and downwardly,respectively. The control panel 30 further includes a “prime” button108, a “start” button 110, and a “stop” button 112. In addition, thecontrol panel 30 may be augmented by a foot switch 114, which includes astop pedal 116, which performs the same function as the stop button 112,and a prime start pedal 118, which performs the same function as theprime button 108 and the start button 110.

Because the blood pump system 24 utilizes feedback from the flowtransducer 48 to maintain and adjust the r.p.m. of the pump 40 in amanner which provides a consistent flow rate, the blood pump system 24requires no user interaction once the system has been primed and theflow rate has been set. Therefore, unlike blood pumps used in otherextracorporeal circuits, the blood pump system 24 may be operated by asemi-skilled technician or nurse, rather than a highly skilledperfusionist.

To provide an extra measure of confidence with such semi-skilledoperation, the blood pump system 24 takes advantage of certain featuresprovided by the interlock system 44. For example, referring to theinterlock system 44 illustrated in FIG. 6 as well, the interlock system44 may include or have access to a personality module 120. Thepersonality module 120 may include a memory 122, such as a read onlymemory for example. The memory 122 of the personality module 120 mayinclude various information, such as flow rates and ranges, as well asother information to be discussed below. Therefore, for a particularpatient or for a particular type of patient, the desired flow rateand/or the desired flow rate range may be programmed into the memory122. For example, in acute myocardial infarction applications, the flowrate may be 75 milliliters per minute, or for stroke applications theflow rate may be 300 milliliters per minute. In this exemplaryembodiment, the personality module 120 may be located in the Y-connector71. Because the information programmed into the personality module 120may be related to a particular patient or a particular type of patient,and because a new Y-connector 71 is typically used with each patient,the location of the personality module 120 in the Y-connector 71provides an effective method of customizing the system 10 with eachpatient treated.

The interlock system 44 reads this flow information from the memory 122and compares it to the flow rate delivered by the flow meter 46 on line124. As long as the flow rate from the flow meter 46 is maintained atthe desired flow rate or within the desired flow range programmed intothe memory 122, the interlock system 44 will continue to supply anenable signal on line 126 to the blood pump system 24. However, shouldthe flow rate fall outside of the desired range, due to operatorintervention, failure of the flow transducer 48, etc., the interlocksystem 44 will switch the signal on the line 126 to disable the bloodpump system 24. The interlock system 44 will further actuate the clamps78 and 80 in order to shut down the system 10 in a manner safe for thepatient 38.

The interlock system 44 includes an analog conditioning circuit 130 thatreceives and conditions the analog flow rate signal from the flow meter46 on the line 124. This conditioned signal is compared with theinformation from the memory 122 using comparators and threshold settings132. The results of this comparison are delivered to a logic block 134,which may be, for example, a field programmable gate array (FPGA) or acomplex programmable logic device (CPLD). The logic block 134 generatesthe enable or disable signal on the line 126.

The conditioning circuit 130 also receives the analog pressure signalsfrom the draw pressure transducer 68 and the return pressure transducer70. These pressures may be monitored to ensure that neither the drawtube 34 nor the return tube 50 are kinked or otherwise unable to deliverfluid at a minimum desired pressure or higher. The logic block 134compares these pressures to the minimum pressure setting, e.g., −300 mmHg, and delivers a warning signal if either pressure drops below theminimum pressure setting. In addition, the draw pressure is monitored toensure that it remains higher than a minimal draw pressure threshold,e.g. −300 mm Hg, to ensure that bubbles are not pulled out of solutionby the blood pump 40. Still further, the return pressure is monitored toensure that it does not exceed a maximum return pressure, e.g. 2000 mmHg.

The manner in which the interlock system 44 interfaces with variousother portions of the system 10 will be discussed below whereappropriate. However, it can be seen that the blood pump system 24 andthe interlock system 44 provide a technique by which blood may beremoved from a patient at a desired and maintainable flow rate and thatany deviation from the desired flow rate will cause the system to shutdown in a manner which is safe for the patient 38. Accordingly, the useof a perfusionist may be obviated in most circumstances.

Oxygenation Device

Although the blood pump system 24 may be used in a variety of differentsystems, for the primary purpose of this discussion it is incorporatedwithin the system 10. As described in reference to FIG. 2 above, one ofits main purposes is to deliver blood to the oxygenation device 54.Accordingly, before discussing the blood pump system 24 or the othercomponents further, an understanding of the manner in which theoxygenation device 54 functions is appropriate.

Referring first to FIGS. 7, 8, and 9, an exemplary embodiment of anoxygenation device 54 is illustrated. As mentioned previously, theoxygenation device 54 includes three chambers: a fluid supply chamber58, an atomization chamber 62, and a mixing chamber 64. Generallyspeaking, physiologic fluid, such as saline, is drawn into the fluidsupply chamber 58. The physiologic fluid is transferred under pressurefrom the fluid supply chamber 58 to the atomization chamber 62. In theatomization chamber 62, the physiologic fluid is enriched with a gas,such as oxygen, to form a gas-enriched physiologic fluid. For example,the physiologic fluid may be supersaturated with the gas. Thegas-enriched physiologic fluid is transferred to the mixing chamber 64to be combined with a bodily fluid, such as blood. The mixing of thegas-enriched physiologic fluid with the bodily fluid forms agas-enriched bodily fluid. In one example, blood from a patient is mixedwith an oxygen-supersaturated saline solution and transmitted back tothe patient.

Beginning with a detailed discussion of the fluid supply chamber 58, anappropriate delivery device, such as a tube 140, is coupled to a supplyof physiologic fluid. In this example, the tube 140 may include a dripchamber 141 and is coupled at one end to an IV bag 56. The other end ofthe tube 140 is coupled to a nozzle 142. The nozzle 142 forms a portionof a fluid passageway 144 that leads to the fluid supply chamber 58. Acheck valve 146 is disposed in the fluid passageway 144 so that fluidmay enter the fluid chamber 58 through the fluid passageway 144, butfluid cannot exit through the fluid passageway 144.

As illustrated by the detailed view of FIG. 10, check valve 146 has anO-ring seal 148 that is disposed between a lip in the fluid passageway144 and the nozzle 142. A spring 150 biases a ball 152 into contact withthe O-ring seal 148. When fluid moving in the direction of the arrow 154overcomes the force of the spring 150 and the pressure within the fluidsupply chamber 58, the ball 152 is pushed against the spring 150 so thatfluid may flow into the fluid supply chamber 58. However, fluid cannotflow in the opposite direction because the ball 152 efficiently sealsagainst the O-ring seal 148.

A piston assembly 160 is disposed at the opposite end of the fluidsupply chamber 58. The piston assembly 160 includes a sleeve 162 that isfixedly disposed within the fluid supply chamber 58. As illustrated ingreater detail in FIG. 11, a plunger 164 is slidably disposed within thesleeve 162. A cap 166 is disposed at one end of the plunger 164. The capincludes a flange 168 that has an outer diameter greater than the innerdiameter of the sleeve 162 to limit downward movement of the pistonassembly 160. Although the sleeve 162, the plunger 164, and the cap 166are advantageously made of a relatively rigid material, such as plastic,a relatively resilient end piece 170 is disposed on the cap 166. The endpiece 170 advantageously includes sealing members 172 that seal againstthe interior walls of the fluid supply chamber 58.

As illustrated by the phantom lines in FIG. 11, the piston assembly 160is moveable between a first position (shown by the solid lines) and asecond position (shown by the phantom lines). To facilitate thismovement, a device to be described below is coupled to the free end 174of the piston assembly 160. Although such coupling may occur in varioussuitable manners, in this example a key 176 is provided at the free end174 of the piston assembly 160. The key 176 includes a narrow portion178 and a relatively wider portion 180 so that it somewhat resembles adoorknob, thus allowing a device to latch onto the piston assembly 160and move it between the first and second positions.

As will be appreciated from a thorough study of this entire discussion,one of the primary advantages of the particular oxygenation device 54disclosed herein involves its sterility and disposability. The sterilityof the piston assembly 160 may be facilitated by providing a sterilitysheath 182 disposed between the cap 166 and the sleeve 162. In thisembodiment, the sterility sheath 182 includes an extendable tube 184that is coupled to the cap 166 by a clamp 186 and coupled to the outerportion of the sleeve 162 by a clamp 188. The expandable tube 184 maytake various forms, such as a plastic tube that folds in anaccordion-like manner when the piston assembly 160 is in its retractedposition (as shown by the solid lines). However, the expandable tube 184may take various other forms, such as a flexible member that stretchesbetween the retracted position and the extended position of the pistonassembly 160. The clamps 186 and 188 may also take various suitableforms, such as rubber O-rings in this example.

Referring additionally to FIG. 12, the fluid supply chamber 58 furtherincludes a second fluid passageway 190. As illustrated by way of aspecific example in the present embodiment, the fluid passageway 190 iscoupled to a fluid passageway 194 by a tube 196. The passageway 194 isan inlet to a valve assembly 200 that controls the manner in which fluidfrom the fluid supply chamber 58 is delivered into the atomizationchamber 62.

In operation, the piston assembly 160 within the fluid supply chamber 58acts as a piston pump. As the piston assembly 160 retracts, fluid isdrawn into the chamber 58 from the fluid supply 56. No fluid can bedrawn from passageway 190 because valve assembly 200 is closed and acheck valve 192 is closed in this direction. As the piston assembly 160extends, the fluid within the chamber 58 is pressurized, typically toabout 670 psi, and expelled from the fluid supply chamber 58 through thefluid passageway 190. The outlet of the fluid supply chamber 58 iscoupled to an inlet of the atomization chamber 62 via an appropriatefluid passageway.

Detailed views of the valve assembly 200 are illustrated in FIGS. 13 and14. The valve assembly 200 includes three valves: a fill valve 202, aflush valve 204, and a flow valve 206. While any suitable valvearrangement and type of valve may be used, in this embodiment the valves202, 204, and 206 are needle valves that are normally biased in theclosed position as shown. When the pressure within the atomizationchamber 62 rises above a certain level, such as about 100 psi, thevalves 202, 204, and 206 will move from the closed position to theopened position, assuming that they are allowed to do so. In thisembodiment, as will be discussed in greater detail below, push pins andassociated actuation mechanisms (as illustrated by the phantom lines inFIG. 13) maintain the valves 202, 204, and 206 in the closed positionsuntil one or more of the valves 202, 204, and 206 is to be opened.

Gas, such as oxygen, is delivered under pressure to the atomizationchamber 62 via a passageway 210. For example, the oxygen tank 60 may becoupled to the inlet of the passageway 210 to provide the desired oxygensupply. If all of the valves 202, 204, and 206 are closed, fluid flowsfrom the inlet passageway 194 into a passageway 212 in which the fillvalve 202 is located. Because the cross-sectional area of the passageway212 is larger than the cross-sectional area of the fill valve 202, thefluid flows around the closed fill valve 202 and into a passageway 214that leads to an atomizer 216.

The atomizer 216 includes a central passageway 218 in which a one-wayvalve 220 is disposed. In this embodiment, the one-way valve 220 is acheck valve similar to that described with reference to FIG. 10.Accordingly, when the fluid pressure overcomes the force of the springin the one-way valve 220 and overcomes the pressure of the gas withinthe atomizer chamber 62, the fluid travels through the passageway 218and is expelled from a nozzle 222 at the end of the atomizer 216.

The nozzle 222 forms fluid droplets into which the oxygen within theatomization chamber 62 diffuses as the droplets travel within theatomization chamber 62. This oxygen-enriched fluid may be referred toherein as aqueous oxygen (AO). In this embodiment, the nozzle 222 formsa droplet cone defined by the angle α, which is typically about 20degrees to about 40 degrees at normal operating pressures, e.g., about600 psi, within the atomization chamber 62. The nozzle 222 is asimplex-type, swirled pressurized atomizer nozzle including a fluidorifice of about 0.004 inches diameter to 0.005 inches diameter. Itshould be appreciated that the droplets infused with the oxygen fallinto a pool at the bottom of the atomizer chamber 62. Since the atomizer216 will not atomize properly if the level of the pool rises above thelevel of the nozzle 222, the level of the pool is controlled to ensurethat the atomizer 216 continues to function properly.

The oxygen is dissolved within the atomized fluid to a much greaterextent than fluid delivered to the atomizer chamber 62 in a non-atomizedform. As previously stated, the atomizing chamber typically operates ata constant pressure of about 600 psi. Operating the atomizer chamber 62at 600 psi, or any pressure above 200 psi, advantageously promotes finerdroplet formation of the physiologic solution from the atomizer 216 andbetter saturation efficiency of the gas in the physiologic fluid thanoperation at a pressure below 200 psi. As will be explained shortly, theoxygen-supersaturated fluid formed within the atomizer chamber 62 isdelivered to the mixing chamber 64 where it is combined with the bloodfrom the patient 38. Because it is desirable to control the extent towhich the patient's blood is enriched with oxygen, and to operate thesystem 10 at a constant blood flow rate, it may be desirable to dilutethe oxygen-supersaturated fluid within the atomizer chamber 62 to reduceits oxygen content. When such dilution is desired, the fill valve 202 isopened to provide a relatively low resistance path for the fluid ascompared to the path through the atomizer 216. Accordingly, instead ofpassing through the atomizer 216, the fluid flows through a passageway230 which extends upwardly into the atomizer chamber 62 via a tube 232.The tube 232 is advantageously angled somewhat tangentially with respectto the cylindrical wall of the atomizer chamber 62 so that the fluidreadily mixes with the oxygen-supersaturated fluid in the pool at thebottom of the atomizer chamber 62.

The valve assembly 200 essentially performs two additional functions.First, with the fill valve 202 and the flow valve 206 closed, the flushvalve 204 may be opened so that fluid flows from the inlet passageway194, through the passageways 212 and 214, and into passageways 240 and242, the latter of which has a cross-sectional area larger than thecross-sectional area of the flow valve 206. Thus, the fluid flows out ofan outlet passageway 244 that is coupled to a capillary tube 246. Thecapillary tube 246 terminates in a tip 248 that extends upwardly intothe mixing chamber 64. Since this fluid has not been gas-enriched, itessentially serves to flush the passageways 242 and 244, and thecapillary tube 246 to remove any contaminants and to ensure adequatefluid flow. Second, with the fill valve 202 and the flush valve 204closed, the flow valve 206 may be opened when it is desired to deliverthe gas-supersaturated fluid from the pool at the bottom of the atomizerchamber 62 into the mixing chamber 64.

In this second circumstance, the gas-supersaturated fluid readily flowsfrom the atomization chamber 62 through the capillary tube 246 and intothe mixing chamber 64 due to the fact that pressure within theatomization chamber 62 is relatively high, e.g., approximately 600 psi,and pressure within the mixing chamber 64 is relatively low, e.g., about30 psi. The end of the capillary tip 248 is advantageously positionedbelow a blood inlet 250 of the mixing chamber 64. This spacialarrangement typically ensures that the blood flowing through the drawtube 34 and into the blood inlet 250 effectively mixes with theoxygen-supersaturated fluid flowing into the mixing chamber 64 throughthe capillary tip 248. Finally, by the force of the blood pump system24, the oxygenated blood is pumped out of the mixing chamber 64 throughan outlet 252 into the return tube 50.

Typically, the capillary tube 246 and the capillary tip 248 arerelatively long to ensure that proper resistance is maintained so thatthe oxygen within the oxygen-supersaturated fluid remains in solution asit travels from the atomization chamber 62 into the mixing chamber 64.For example, the capillary tube 246 and the tip 248 may be in the rangeof 50 microns to 300 microns in length and in the range of 3 inches to20 inches in internal diameter. To maintain the compact size of theoxygenation device 54, therefore, the capillary tube 246 is wrappedabout the exit nozzle 252 of the mixing chamber 64, as illustrated inthe detailed drawing of FIG. 15. To protect the coiled capillary tube246 from damage, a protective shield 254 is advantageously formed aroundthe coiled capillary tube 246 to create a compartment 256.

Both the atomization chamber 62 and the mixing chamber 64 include ventvalves 258 and 260, respectively. The vent valves 258 and 260, asillustrated in the detail drawing of FIG. 16, are one-way valves thatallow gas pressure to be vented out of the oxygenation device 54 andinto the atmosphere. In this particular embodiment, the vent valves 258and 260 include a plunger 262 that is biased in a closed positionagainst an O-ring seal 264 by a spring 266. The biasing force is lightso that only one to two psi within the respective chambers 62 or 64 issufficient to move the plunger 262 away from the seal 264 to vent thechamber. Therefore, as will be discussed in greater detail below,actuation devices that are part of the cartridge enclosure 26 andcontrolled by the system controller 55 normally maintain the valves 258and 260 in the closed position.

Before beginning a discussion of the remainder of the system 10, a fewpoints regarding oxygenation of blood in general, and the use of thedisclosed oxygenation device 54 in particular, should be noted. First,various methods of oxygenating blood are known or under development.Although an atomizing chamber provides a convenient mechanism fordiffusing relatively large amounts of gas into a fluid in a relativelyshort period of time, it is not the only way of dissolving gas within afluid. Indeed, other devices, such as membrane oxygenators, gasspargers, bubblers, and thin film oxygenation devices, may be used toperform this function as well. Second, although a piston pump similarlyprovides a compact and efficient method of pressurizing fluid prior tosending it to an oxygenator, such as the atomizer, other types of pumpsor methods of pressurization may be used as well. Third, although amixing chamber provides a compact environment in which the mixing of thegas-supersaturated fluid with blood may be appropriately monitored andcontrolled, gas-enriched fluid may be mixed with blood in other ways.For example, gas-supersaturated fluid may be mixed with blood within themixing zone of a catheter or other suitable device. Therefore, althougha piston pump, atomizer, and mixing chamber comprise the oxygenationdevice 54 utilized in the exemplary embodiment of the system 10, due tocertain perceived advantages, other devices can, generally speaking,perform these functions.

With these generalities in mind, the oxygenation device 54 disclosedherein offers several advantages that make it particularly attractivefor use within a medical environment. First, the oxygenation device 54is advantageously made from a clear plastic, such as polycarbonate whichcan be molded to provide a high strength, low cost device. Second, theoxygenation device 54 is relatively compact, with an exemplary specimenmeasuring approximately 12 cm in height, 10 cm in width, and 5.5 cm indepth. Thus, it can be utilized within a system 10 that fits easilywithin an operating room or special procedures lab, regardless ofwhether the system 10 is fixed or mobile. Third, the oxygenation device54 combines the preparation of the oxygen-enriched fluid, along with themixing of the oxygen-enriched fluid with the blood, into a unitarydevice utilizing only four connections: (1) fluid supply, (2) oxygensupply, (3) blood supply, and (4) blood return. The other connectionsare part of the oxygenation device 54 itself, and they require noadditional connection from the user. Fourth, all of the valves used tooperate the oxygenation device 54 are integrated within its unitarystructure. Thus, the valves and their associated fluid passageways areprotected against external contamination, and users are protectedagainst any contamination that may arise from the use of the variousfluids as well. As a result, the oxygenation device 54 is a relativelycontamination-free cartridge that may be used during a surgicalprocedure on a patient, and then removed and replaced prior toperforming a surgical procedure on the next patient.

Cartridge Enclosure

Prior to discussing the remainder of the electrical components and themanner in which they control the various mechanical components of thesystem 10, the manner in which certain mechanical components interfacewith the oxygenation device 54 will now be discussed. As mentionedpreviously, the oxygenation device 54 is placed inside of the cartridgeenclosure 26. FIG. 17 illustrates an exploded view of the cartridgeenclosure 26, and FIG. 18 illustrates a front view of the cartridgeenclosure 26. In this embodiment, the cartridge enclosure 26 includes acartridge receptacle 302 that is accessed by a hinged door 304. When theoxygenation device 54 is placed within the cartridge receptacle 302, thedoor 304 is closed and latched for various reasons. First, the cartridgereceptacle 302 and the oxygenation device 54 are sized and shaped in acomplementary fashion so that the various surfaces, vents, valves, etc.are positioned in a desired manner. When the door 304 is closed andlatched, an inner surface 306 of the door 304 advantageously pressesagainst a surface 308 of the oxygenation device 54 to ensure that thepositioning of the oxygenation device 54 is accurate. Second, the door304 is advantageously locked to prevent removal of the oxygenationdevice 54 during normal operation of the system 10. Accordingly, thedoor 304 is provided with a latch 310. Referring to FIGS. 19-26, thedoor latch 310 includes a handle portion 312 and a latching portion 314.

To latch the door 304, a user grasps the handle portion 312 to pivot thelatch 310 about a pivot pin 316 generally in the direction of the arrow318. As the latch 310 pivots in the direction of the arrow 318, thelatching portion 314 hooks around a latch pin 320. The latch pin 320 iscoupled to a biasing mechanism 322. The biasing mechanism 322, in thisembodiment, includes two pins 324 and 326 that extend through holes in awall 328. A respective spring 330 and 332 is disposed about each pin 324and 326 to bias the latch pin 320 toward the wall 328. As the latchingportion 314 hooks around the latch pin 320, the latch 310 may tend toovercome the bias of the springs 330 and 332 to move the latchingmechanism 322 slightly in the direction of the arrow 334. However, dueto the bias of the latching mechanism 322, it tends to hold the latch310, and thus the door 304, tightly in place.

To keep the latch 310 in place, and thus lock the door 304, a lockingmechanism 340 is provided. In this embodiment, the locking mechanismincludes 340 a slidable pin 342 that is disposed in a portion of thewall 328. As the latch 310 moves in the direction of the arrow 318, iteventually contacts the front end of the pin 342, and thus moves it inthe direction of the arrow 344. The rear portion of the pin 342 iscoupled to a piston 346 of a pull-type solenoid 348. The piston 346 isbiased outwardly by a spring 350, so that the piston 346 is normally inan extended position.

The latch 310 is configured so that as it reaches its latched position,the spring 350 pushes the pin 342 in the direction of the arrow 352 sothat the pin 342 extends over a portion 354 of the latch 310. With thepin 342 in its locked position over the portion 354 of the latch 310,the latching portion 314 cannot be removed from the latching mechanism322. Instead, the latch 310 remains locked until the piston 346 of thesolenoid 348 is retracted to move the pin 342 out of the way of thelatch 310.

It should also be noted that the latch 310 includes a sensor 360 thatprovides an electrical signal indicative of whether the latch 310 is inits locked position. In this embodiment, the sensor 360 is a Hall effectsensor. The latch 310 includes a magnet 362 that is positioned to alignwith the sensor 360 when the latch 310 is in the locked position. Whenthe magnet 362 is aligned with the sensor 360, the electromagneticsignal is uninterrupted. However, until the magnet 362 reachesalignment, the electromagnetic signal from the sensor 360 isinterrupted, thus indicating that the latch 310 is not yet in its lockedposition.

Valve Actuation

As mentioned previously, in the present embodiment, the size and shapeof the oxygenation device 54, the contour of the cartridge receptacle302, and the closing of the door 304 ensure that the oxygenation device54 is positioned in a desired manner within the cartridge enclosure 26.Correct positioning is of concern due to the placement of the valves andvents of the oxygenation device 54 and the manner in which they arecontrolled and actuated. As mentioned earlier, the valves and vents ofthe oxygenation device 54 are actuated using pins in this embodiment.The top of the oxygenation device 54 includes vents 258 and 260, and thebottom of the oxygenation device 54 includes three valves, 202, 204, and206. In this embodiment, these vents 258 and 260 and valves 202, 204 and206 are electromechanically actuated using solenoid-actuated pins.

A detailed view of these actuation devices is illustrated in FIGS.27-32. Referring first to FIG. 27, a bottom view of the cartridgeenclosure 26 is illustrated. The oxygenation device 54 is illustrated byphantom lines. It should be noted that the bottom portion of thecartridge enclosure 26 advantageously includes a slot 380 through whichthe blood return tube 50 of the oxygenation device 54 may pass. Once theoxygenation device 54 is in place within the cartridge enclosure 26, thefill valve 202, the flush valve 204, and the flow valve 206 should be inalignment with respective actuation pins 382, 384, and 386.Advantageously, each of the pins 382, 384, and 386 is tapered at the endto provide an increased tolerance for misalignment. Each of theactuation pins 382, 384, and 386 is moved between a closed position andan open position by a respective solenoid 388, 390, and 392. Each of thesolenoids 388, 390, and 392 is coupled to its respective actuation pin382, 384, and 386 via a respective lever 394, 396, and 398. Each of therespective levers 394, 396, and 398 pivots on a respective fulcrum orpivot pin 400, 402, and 404.

The manner in which the actuators operate may be understood withreference to FIGS. 28 and 29. While these figures only illustrate theactuator for the flush valve 204, it should be understood that the otheractuators operate the fill valve 202 and the flow valve 206 in the samemanner. As mentioned previously, the valves 202, 204, and 206 arenormally held in a closed position. Accordingly, in this particularembodiment, the solenoids 388, 390, and 392 are pull-type solenoids. Asillustrated in FIG. 28, a piston 406 of the pull-type solenoid 390 isurged into an extended position by a spring 408 that biases one end ofthe lever 396 generally in the direction of the arrow 410. As a result,the spring 408 also biases the actuation pin 384 generally in thedirection of the arrow 412 to maintain the flush valve 204 in its closedposition.

To allow the flush valve 204 to open, the solenoid 390 is actuated asillustrated in FIG. 29. The actuation of the pull-type solenoid 390moves the piston 406 generally in the direction of the arrow 414 into aretracted position. The force of the solenoid 390 overcomes the bias ofthe spring 408 and moves the actuation pin 384 generally in thedirection of the arrow 416. With the actuation pin 384 in a retractedposition, the flush valve 204 may open by moving in the direction of thearrow 416.

The actuation of the vent valves 258 and 260 takes place in a similarfashion. Referring now to FIG. 30, a top view of the cartridge enclosure26 is illustrated. The top portion of the cartridge enclosure 26 alsoincludes a slot 420 through which the IV tube 140 may pass. Once theoxygenation device 54 is properly positioned within the cartridgeenclosure 26, the vent valves 258 and 260 align with actuation pins 422and 424, respectively. The pins 422 and 424 are also advantageouslytapered at the ends to increase tolerance to misalignment. Each of theactuation pins 422 and 424 is actuated by a respective solenoid 426 and428. Each of the solenoids 426 and 428 is coupled to the respectiveactuation pin 422 and 424 by a respective lever 430 and 432. Each of thelevers 430 and 432 pivots about a fulcrum or pivot pin 434 and 436,respectively.

As described with reference to FIGS. 31 and 32, the operation of theactuators for the valves 258 and 260 is similar to the operation of theactuators for the valves 202, 204, and 206. Although FIGS. 31 and 32illustrate only the actuator for the vent valve 260, it should beunderstood that the actuator for the vent valve 258 operates in asimilar manner. Referring first to FIG. 31, the solenoid 428 in thisembodiment is a pull-type solenoid. A spring 440 generally biases thelever arm 432 in the direction of the arrow 442 to move a piston 444 ofthe solenoid 428 into an extended position. Accordingly, by virtue ofthe action of the lever 432 about the pivot pin 436, the spring 440moves the actuation pin 424 into an extended position. In the extendedposition, the actuation pin 424 exerts pressure on the vent valve 260(not shown) to maintain the vent valve 260 in a closed position.

To open the vent valves 258 and 260, the solenoids 426 and 428 areactuated. As illustrated in FIG. 32, when the pull-type solenoid 428 isactuated, the piston 444 moves into a retracted position generally inthe direction of the arrow 446. The force of the solenoid 428 overcomesthe biasing force of the spring 440 and, thus, the lever 432 moves theactuation pin 424 generally in the direction of the arrow 448 into aretracted position. When the actuation pin 424 is in the retractedposition, the vent valve 260 may move upwardly to open and vent gaswithin the mixing chamber 64.

Cartridge Sensors

Referring again to FIG. 18, a study of the cartridge receptacle 302reveals that a number of sensors are utilized to monitor and/or controlthe system 10 in general and the oxygenation device 54 in particular.Due to the nature of the information to be gathered and the types ofsensors used to gather this information, the oxygenation device 54 andthe sensors include certain features that facilitate the gathering ofsuch information in a more accurate and robust manner. However, itshould be appreciated that other types of sensors and/or features may beutilized to gather similarly relevant information for use in monitoringand/or controlling the system 10 and oxygenation device 54.

As will be appreciated from a detailed discussion of the electroniccontrols of the system 10, it is desirable to monitor and control fluidlevels within the atomization chamber 62 and the mixing chamber 64.Accordingly, an AO level sensor 480 is provided to monitor the level ofaqueous oxygen within the atomizer chamber 62, and a high level sensor482 and a low level sensor 484 are provided to monitor the level of theoxygen-enriched blood within the mixing chamber 64. As mentioned above,because the oxygenation device 54 is configured as areplaceable-cartridge in this exemplary embodiment, the sensors havebeen placed within the cartridge enclosure 26 instead of within theoxygenation device 54. Thus, the level sensors 480, 482, and 484 do notactually contact the fluid within the chambers 62 and 64. Were thesensors 480, 482, and 484 to contact the liquid, they could becomecontaminated and, thus, the sensors would typically be replaced eachtime the system 10 was used for a different patient. Since this wouldlikely add to the cost of replacement items, and potentially affect thesterility of the system, from both a user's standpoint and a patient'sstandpoint, it is desirable that the sensors do not contact the liquidwithin the oxygenation device 54.

In this embodiment, the sensors 480, 482, and 484 are ultrasonicsensors. Because ultrasonic waves travel more efficiently through solidsand liquids than through air, it is desirable that the sensors 480, 482,and 484 and/or the oxygenation device 54 be configured in a manner whichpromotes the efficient transmission and reception of ultrasonic waves.In this embodiment, both the sensors 480, 482, and 484 and theoxygenation device 54 include features which prove advantageous in thisregard.

FIGS. 19 and 33 are cross-sectional views of the cartridge enclosure 26that illustrate the high level sensor 482 and the AO level sensor 480,respectively. Although the low level sensor 484 is not illustrated incross-section, it should be understood that its construction is similarto or identical to the construction of the sensors 480 and 482.Furthermore, detailed views of the sensors 482 and 480 are illustratedin FIGS. 34 and 35, respectively, again with the understanding that thesensors 480, 482, and 484 are substantially identical in regard to thedetails shown in these FIGS.

To ensure that physical contact is maintained between the oxygenationdevice 54 and the sensors 480, 482, and 484, the sensors areadvantageously biased into contact with the oxygenation device 54. Thesensors 480, 482, and 484 actually utilize a spring-biasing technique,although various other types of biasing techniques may be utilized toachieve similar results. In this example, an ultrasonic transducerelement 490 is disposed within a channel 492 formed within a sensor body494. The sensor body 494 may be formed in any suitable shape, but it isillustrated in this embodiment as being cylindrical. The sensor body 494is slidably disposed within a sleeve 496. The sleeve 496 is fixedlydisposed in a wall 498 of the cartridge enclosure 26. For example, thesleeve 496 may have external screw threads 500 so that the sleeve 496may be screwed into a threaded bore in the wall 498. To facilitateslidable movement of the sensor body 494 within the sleeve 496, abushing 502 may be provided,within the sleeve 496. In this example, thesensor body 494 includes an annular flange 504 that abuts against oneend of the bushing 502 in order to limit outward movement of the sensorbody 494. A spring 506 is disposed in the rear portion of the sleeve496. The spring 506 abuts against the opposite side of the annularflange 504 to bias the sensor body 494 generally in the direction of thearrow 508. The bushing 502 may be adhered to, or an integral part of,the sleeve 496, or it may be held in place by an external seal or cap510.

Although the spring-loaded construction of the sensors 480, 482, and 484tends to bias the sensors into contact with the oxygenation device 54 tofacilitate the efficient transmission of ultrasonic energy, the natureof the contact between the end of the sensor and the oxygenation device54 is also important for efficient ultrasonic wave transmission. Hence,to improve this contact region, the sensors 480, 482, and 484 include aresilient member 512, such as a rubber cap. The resilient member 512 isable to deform slightly as it contacts the oxygenation device 54 toensure that a good contact is made. To enhance the contact regionfurther, the oxygenation device 54 advantageously includes flat contactportions 514 and 516, respectively, so that the contour of theoxygenation device 54 matches the contour of the resilient member 512.In addition, to enhance the ultrasonic contact even further, a suitablegel may be used between the oxygenation device 54 and the sensors 480,482, and 484.

The cartridge enclosure 26 advantageously includes other sensors aswell. For example, it may be desirable for the system 10 to be able todetermine whether the oxygenation device 54 has been inserted within thecartridge enclosure 26. To provide this information, a cartridge presentsensor 520 may be disposed within the cartridge enclosure 26. In thisexample, the cartridge present sensor 520, as illustrated in FIG. 19,may be a reflective infrared sensor that is positioned within an opening522 in the wall 498 of the cartridge enclosure 26. Unlike the ultrasonicsensors discussed previously, the efficiency of a reflective infraredsensor is not improved by physical contact. Indeed, the efficiency of areflective infrared sensor relates more to the nature of the surfacereflecting the infrared energy back to the sensor. In other words, ifthe surface is irregular, the infrared energy transmitted from theinfrared sensor may scatter so that little or no infrared energy isreflected back to the sensor. On the other hand, if the surface issmooth, generally perpendicular to the sensor, and/or reflective, ittends to maximize the amount of infrared energy reflected back to thesensor. Accordingly, the portion of the oxygenation device 54 positionedadjacent the cartridge present sensor 520 is advantageously configuredto promote reflection of infrared energy back to the cartridge presentsensor 520. In this example, the oxygenation device 54 advantageouslyincludes a flat section 524 to ensure that the cartridge present sensor520 receives a relatively strong reflective signal so that it canproperly indicate whether the oxygenation device 54 is present.

It may also be desirable to monitor the temperature of the aqueousoxygen formed within the atomizer chamber 62. The temperature of theaqueous oxygen is a useful parameter because the oxygenation level ofthe aqueous oxygen, and ultimately the oxygenation level of theoxygen-enriched blood, may vary with temperature. If it is desirable totake a temperature measurement into account to monitor and control thefunctioning of the oxygenation device 54 and the system 10, thetemperature may be sensed in a variety of different areas. For example,a simple room temperature sensor may be incorporated somewhere withinthe system 10, using the assumption that the physiologic solution to beoxygenated will typically be at room temperature. Alternatively, thetemperature of the oxygenation device 54 may be monitored, using theassumption that the aqueous oxygen within the oxygenation device 54 willbe at the same temperature.

However, to provide the greatest level of control, it may be desirableto measure the temperature of the aqueous oxygen within the atomizerchamber 62. Although a thermocouple could be disposed in the atomizerchamber 62 of the oxygenation device 54 with appropriate electricalcontacts extending out of the oxygenation device 54, the use of a sensorwithin a disposable device would only increase the cost of the device.Accordingly, it may be desirable to utilize a sensor that is external tothe atomizer chamber 62 and yet still able to monitor the temperature ofthe aqueous oxygen within the atomizer chamber 62. To achieve thisfunction in this example, an external temperature sensor 540 is coupledwithin an opening 542 in the wall 498 of the cartridge enclosure 26 asillustrated in FIG. 33. The temperature sensor 540 may be, for example,a pyroelectric sensor or a piezoelectric sensor. Changes in thetemperature of the AO solution within the atomizer chamber 62 will alterthe frequencies of such signals and, thus, indicate the actualtemperature of the AO solution.

Gas Coupling

The cartridge enclosure 26 also includes another interesting featureregarding the manner in which it interfaces with the oxygenation device54. As previously discussed, the oxygenation device 54 includes anoxygen inlet 210 located near the top of the atomizer chamber 62. Asalso previously mentioned, a supply of oxygen 60 regulated to about 600psi is coupled to the oxygen inlet 210. Thus, it may be desirable toprovide a connection to the inlet 210 that effectively handles suchpressure and does not require user intervention.

Referring to FIG. 36, the oxygen supply 60 is typically enabled by aflow valve 600. The flow valve 600 delivers oxygen through a pressuretransducer 602 and a check valve 604. The oxygen then proceeds through atee 606 and into a line 608. The line 608 is coupled to a plunger 610illustrated in the cross-sectional view of FIG. 37. The plunger 610includes a port 612 that runs laterally from the line 608 and thendownwardly into the cartridge cavity 302. The plunger 610 is slidablydisposed within a bushing or sleeve 614. As best illustrated in thedetailed views of FIGS. 38 and 39, the sleeve 614 includes a recessedarea 616 in which a spring 618 is disposed. The spring tends to bias theplunger 610 upwardly so that the coupling portion 620 of the plunger 610that is configured to seal against the oxygen inlet 210 of theoxygenation device 54 is recessed slightly.

The top of the plunger 610 includes a slanted or cammed portion 622 thatabuts in a complimentary relationship with a slanted or cammed portion624 of a rod 626. The rod 626 is slidably disposed within an opening 628in the cartridge enclosure 26. The rod 626 is biased in the direction ofthe arrow 630 in an extended position by a spring 632. As bestillustrated in FIG. 39, when a user closes the door 304, the rod 626 ismoved in the direction of the arrow 634 against the bias of the spring632. As the rod 626 moves back against the spring 632, the cammedsurfaces 622 and 624 slide against one another, thus forcing the plunger610 downwardly in the direction of the arrow 636 to seal the couplingportion 620 against the oxygen inlet 210. The rod 624 is advantageouslyprovided with an adjustment screw 638. The adjustment screw 638 may beadjusted so that the abutment portion 640 of the rod 626 is in anappropriate position to ensure that the coupling portion 620 of theplunger 610 solidly seals against the oxygen inlet 210 when the door 304is closed and latched.

Piston Drive Mechanism

To this point in the discussion, all of the various interfaces betweenthe cartridge receptacle 302 and the oxygenation device 54 have beendiscussed with the exception of one. As mentioned previously, theoxygenation device 54 includes a piston assembly 160 that is configuredto draw physiologic solution into the chamber 58 and to deliver it underpressure to the atomization chamber 62. As illustrated in FIG. 8, theplunger 164 includes a key 176 at one end. As mentioned during thatdiscussion, the key 176 is configured to fit within a key slot of adevice that moves the piston assembly 160 between its extended andretracted positions.

Although a variety of different mechanisms may be used to achieve thisfunction, the drive mechanism utilized in the present embodiment isillustrated in FIG. 40 and generally designated by the reference numeral700. Generally speaking, the drive mechanism 700 includes a ball screwmechanism 702 that is driven and controlled by a motor 704. In thisembodiment, the motor 704 is a stepper motor whose position is monitoredby an optical encoder 706. Although the motor 704 may be directlycoupled to the ball screw mechanism 702, a transmission 708 is used totransfer power from the motor 704 to the ball screw mechanism 702 inthis embodiment. Specifically, an output shaft 710 of the motor 704 iscoupled to a gear 712. The gear 712 meshes with a gear 714 that isoperatively coupled to turn a screw 716. In this embodiment, the gears712 and 714 have a drive ratio of one to one. However, any suitabledrive ratio may be used.

As the motor 704 turns the screw 716, a “drive” assembly 718 rides up ordown the screw 716 generally in the direction of the arrow 720 dependingupon the direction of rotation of the screw 716. A ram 722 is slidablydisposed about the screw 716 at the top of the drive assembly 718. Theram 722 includes a key way 724 that is configured to accept the key 176of the piston assembly 160. Hence, as the ram 722 moves up and down withthe drive assembly 718 in response to rotation of the screw 716, itmoves the piston assembly 160 back and forth within the chamber 58.

The drive assembly 718 advantageously includes a load cell 726 that isloaded as the ram 722 extends to drive the piston assembly 160 into thechamber 58. The force exerted on the load cell 726 relates to the fluidpressure within the chamber 58 when the piston assembly 160 is drivingfluid out of the passageway 190. Accordingly, the reading from the loadcell 726 may be used to control the speed and position of the ram 722 toensure that fluid is delivered to the atomization chamber 62 at thedesired pressure.

The components of the stepper motor assembly 700 are more clearlyillustrated in the exploded view of FIGS. 41A and 41B. In addition tothe components previously discussed, it can be seen that the gears 712and 714 ride on respective bearings 730 and 732. The motor 704 ismounted to one side of a bracket 734, while a shroud 736 that surroundsthe drive assembly 718 is mounted on the other side of the bracket 734.It can further be seen that the screw 716 is mounted within a coupling738 that rides on a tapered thrust bearing 740. The thrust bearing 740is useful for accommodating the force of thrusting the ram 722 upwardlyto drive the piston assembly 160 into the chamber 58.

The drive assembly 718 includes a nut 742 that is threadably coupled toa load cell mount 744. Referring additionally to the cross-sectionalview of FIGS. 42 and 43, the load cell mount 744 includes a slot 746having a closed end. When the load cell mount 744 is placed within theshroud 736, the slot 746 is aligned with a set pin 748. The set pin 748is disposed within the slot 746 to prevent the drive assembly 718 frombottoming out as it moves downwardly in response to rotation of thescrew 716. Instead, the drive assembly 718 stops when the end of theslot 746 meets the set pin 748.

It should also be appreciated that the drive assembly 718 should moveaxially, not rotationally, in response to rotation of the screw 716. Toaccomplish such movement, a guide 737 is disposed on the inner wall ofthe shroud 736. The guide 737 interfaces with a slot 747 in the loadcell mount 744 to prevent rotation of the drive assembly 718 as it movesup and down along the screw 716. Rather, because the drive assembly 718is prevented from rotating, it moves axially relative to the screw 716.

The lower end of the ram 722 includes a flange 750. The flange 750impinges upon the top portion of a load cell cover 752, and a lock ring754 is coupled to the bottom of the ram 722 to fix the load cell 726 andthe load cell cover 752 onto the ram 722. The load cell cover 752 isfurther coupled to the load cell mount 744 by a screw 756. Finally, theupper end of the ram 722 is placed through a bearing 758, and a coverplate 760 is screwed onto the top of the shroud 736.

The stepper motor assembly 700 further includes a sensor assembly 800 asillustrated in FIGS. 44-48. The sensor assembly 800 provides two signalsto the system controller 55. The first signal is generated when thedrive assembly 718, and thus the piston assembly 160, has reached itsmaximum travel, i.e., its maximum extension. The second signal isprovided when the drive assembly 718, and thus the piston assembly 160,reaches its home position, i.e., maximum retraction. The maximum travelsignal is useful to ensure that the cap 166 of the piston assembly 160does not bottom against the end of the chamber 58. The home positionsignal is useful for resetting the optical encoder 706 so that it canstart monitoring the motor 704 from a known position of the driveassembly 718.

As illustrated in FIGS. 44 and 46, the sensor assembly 800 includes amaximum travel sensor 802 and a home position sensor 804. In thisembodiment, the sensors 802 and 804 are optical sensors. Thus, as bestillustrated in FIG. 48, each of the sensors 802 and 804 includes anoptical transmitter 806 and an optical receiver 808. So long as the pathbetween the optical transmitter 806 and optical receiver 808 remainsclear, the optical receiver 808 receives the optical signal transmittedfrom the optical transmitter 806. However, if an obstruction comesbetween the optical transmitter 806 and the optical receiver 808,/theoptical receiver 808 does not receive the optical signal sent from theoptical transmitter 806. Thus, the output of the optical sensor 802 or804 will change in this circumstance to indicate that an obstruction ispresent.

In the present embodiment of the sensor assembly 800, a tab or flag 810is coupled to the load cell mount 744, as best illustrated in FIG. 47.In this embodiment, screws 812 and 814 are used to couple the flag 810to the load cell mount 744, although any suitable mounting arrangementmay be utilized. FIGS. 46 and 47 illustrate the drive assembly 718 inthe home position. Accordingly, the flag 810 is positioned between theoptical transmitter 806 and the optical receiver 808 of the homeposition sensor 804.

General System Operation

Now that the various mechanical components of the system 10 have beendiscussed, the manner in which the system 10 operates under the controlof various electrical components may now be discussed. Turning now toFIG. 49, a state diagram 900 depicts the basic operation of thisembodiment of the system 10.

When the system 10 is powered on or reset, it enters an initializationmode 902. In the initialization mode, the system controller 55 setsvarious system parameters and performs various diagnostic checks. Forexample, if the system 10 was powered down improperly the last time itwas turned off, an error code may be provided. Furthermore, if thesystem 10 experiences a. watchdog timer failure, which typically meansthat its processor is lost or not functioning properly, the system willenter a watchdog failure mode 904.

In the initialization mode 902, the system controller 55 also reads thecartridge present signal delivered by the sensor 520. As illustrated inFIG. 50, the cartridge present signal is processed by an IO registersubsystem 906 prior to processing by the CPU 908. If an oxygenationdevice 54 is present within the cartridge enclosure 26, the systemswitches from the initialization mode 902 into an unload mode 910. Inthe unload mode 910, the oxygenation device 54 is depressurized and thedoor is unlocked to allow removal of the oxygenation device 54. Removalof a used oxygenation device 54 is desirable to ensure that the sameoxygenation device 54 is not used for multiple patients. To depressurizethe oxygenation device 54, the system controller 55 delivers an O₂ ventsignal 912 to the solenoid 426 associated with the atomizer chamber 62and a blood mixing chamber vent signal 914 to the solenoid 428associated with the mixing chamber 64. As discussed previously, thesolenoids 426 and 428 respond by retracting the respective pins 422 and424 to enable the vent valves 258 and 260 to open. Once the oxygenationdevice 54 has been depressurized, the system controller 55 disables adoor lock signal 916 which causes the solenoid 348 to retract andwithdraw the locking pin 342 from the door latch 310.

If the user does not unload the oxygenation device 54 within 30 seconds,a timeout occurs and the system 10 switches into a wait state 920,labeled wait mode 3. In the wait mode 3 state 920, an unload commandwill continue to be delivered so that the system 10 switches between theunload mode 910 and the wait mode 3 state 920 until the user hascompleted the unload operation. Then, when the oxygenation device 54 isnot present, the system switches from the wait mode 3 state 920 backinto the initialization mode 902.

Once initialization is complete, the system 10 switches into a wait mode1 state 922. In the wait mode 1 state 922, the system controller 55monitors a RS232 serial communications port 924 to await a load commandfrom the host/user interface 66. Upon receipt of the load command, thesystem 10 switches into a load mode 926. The load mode 926 allows a userto install a new oxygenation device 54 and to prepare the system forpriming. In the load mode 926, all valve actuation pins 382, 384, 386,422, and 424, as well as the door lock pin 342, are retracted.Retraction of the valve actuation pins is desirable because the extendedactuation pins may inhibit the oxygenation device 54 from beinginstalled properly within the cartridge enclosure 26. To retract therespective valve actuation pins 382, 384, 386, 422, and 424, as well asthe door lock pin 342, the system controller 55 delivers a fill signal930, a flush signal 932, an AO flow signal 934, an O₂ vent signal 912, ablood mixing chamber vent signal 914, and a lock signal 916, to thesolenoids 388, 390, 392, 426, 428, and 348, respectively.

Like the unload mode 910 described previously, the load mode 926 alsoincludes a timer, such as a 30 second timeout, which causes the system10 to revert from the load mode 926 back to the wait mode 1 state 922 ifthe user has not loaded the oxygenation device 54 in the allotted time.However, once the user has successfully loaded the oxygenation device 54within the cartridge enclosure 26 as indicated by the cartridge presentsignal 520, the valve actuation pins 382, 384, 386, 422, and 424, aswell as the door lock pin 342, are all extended so that the respectivevalves 202, 204, 206, 258, and 260 are held in their closed positions,and so that the latch 310 will lock when the door 304 is closed.

Once the door 304 has been closed and locked, the load operation iscomplete, and the system 10 switches from the load mode 926 into a waitmode 2 state 940. In the wait mode 2 state 940, the system controller 55monitors the RS232 serial communications port 924 to await either aprime command or an unload command. If the unload command is received,the system 10 transitions into the unload mode 910, which operates aspreviously discussed. However, if the prime command is received, thesystem 10 transitions into a prime mode 942.

A user initiates the prime mode 942 by pressing the prime switch 108. Inthe prime mode 942, the system 10 fills the fluid supply chamber 58 withphysiologic solution and drives the piston assembly 160 to pressurizethe solution and transfer it into the atomizer chamber 62 until theappropriate level of fluid is reached. In the prime mode 942, a steppermotor drive subsystem 950 of the system controller 55 reads the positionof the stepper motor 704 from the encoder 706 and drives the steppermotor 704 to cause the ram 722 to push the piston assembly 160 into itsfully extended position within the fluid supply chamber 58. As thepiston assembly 160 is retracted, physiologic solution is drawn into thefluid supply chamber 58 through the passageway 144. The piston assembly160 then extends again to pressurize the physiologic solution within thefluid supply chamber 58 and to transfer it from the fluid supply chamber58 into the atomizer chamber 62. In this mode, the fill valve 202 isopened, so that the fluid enters the atomizer chamber 62 through thetube 232 rather than through the atomizer 216.

When the system controller 55 receives the signal from the AO levelsensor 480 indicating that the atomizer chamber 62 has beenappropriately filled, the stepper motor driver subsystem 950 retractsthe piston assembly 160 to the home position and then extends the pistonassembly 160 to transfer an additional amount of solution, e.g., 3 ccs,into the atomizer chamber 62. After the atomizer chamber 62 has beenprimed with the physiologic solution, the system controller 55 deliversan O₂ flow signal 952 to an O₂ flow solenoid 954 to open a valve 956 andallow the oxygen from the supply 60 to pressurize the atomizer chamber62.

Once the proper level of fluid has been reached, the prime mode 942 iscomplete. However, prior to completion of the priming operation, thesystem 10 may transfer from the prime mode 942 to the wait mode 2 state940 if the priming operation is interrupted by a halt commandtransmitted as either a result of an error in the priming operation oras a result of the user pressing the stop switch 112.

Once the prime mode 942 is complete, the system 10 transitions into anAO off mode 960. While in the AO off mode 960, no aqueous oxygen isproduced or delivered. Instead, the system controller 55 delivers aflush signal 932 to the solenoid 390 to open the flush valve 204. Aspreviously discussed, when the flush valve 204 is open, physiologicsolution flows from the fluid supply chamber 58 through the valveassembly 200 and into the mixing chamber 64 through the capillary tube246. This mode of delivery continues so long as the blood flow throughthe mixing chamber 64 is above a predetermined rate, e.g., 50 ml perminute. If the blood flow drops below the predetermined rate, the system10 transitions into a timeout mode 962. In the timeout mode 962, thesystem 10 does not flow, fill, or flush, and the piston assembly 160returns to the home position. The system 10 will transition from thetimeout mode 962 to the unload mode 910 if either the unload command isreceived from the host/user interface 66 or if the system 10 has been inthe timeout mode 962 for a predetermined time, e.g., 150 seconds.However, once blood flow rises above the predetermined rate, the system10 transitions from the timeout mode 962 back to the AO off mode 960.

When the AO on command is received, the system 10 transitions from theAO off mode 960 to an AO on mode 964. The AO on command is produced whenthe user presses the prime button 108 and the start button 110simultaneously. In the AO on mode 964, the priming signal is deliveredfrom the blood pump system 24 on a line 966 to the interlock system 44.If the system controller 55 is in the AO off mode 960 when the primecommand is received, then the logic block 134 of the interlock system 44delivers an enable signal on line 126 to enable the blood pump 24. Thelogic block 134 also delivers a draw clamp signal on a line 970 to thedraw clamp 78 to open it while the return clamp 80 remains closed. Thelogic block 130 also delivers a prime signal on a line 968 to the CPU908 of the system controller 55. In response to receiving the primesignal, the system controller 55 monitors the low level sensor 484 todetermine when enough blood has flowed into the mixing chamber 64 forthe chamber to be filled to the level indicated by the low level sensor484. The low level signal is also sent to the logic block 134 of theinterlock system 44 via a line 974. When the interlock system 44determines that the chamber 64 has been filled to the level indicated bythe low level sensor 484, it delivers a return clamp signal on a line972 to the return clamp 80 to open it. Simultaneously, the systemcontroller 55 delivers a cyclox vent signal 914 to the solenoid 428 inorder to close the vent valve 260.

The system 10 continues to operate in the AO on mode 964 in this mannerunless blood flow drops below a predetermined rate, e.g., 50 ml. perminute. In this instance, the system 10 will transfer from the AO onmode 964 to the unload mode 910, which will operate as discussedpreviously.

The logic block 134 of the interlock system 44 also delivers an AOenable signal on a line 976 to the CPU 908 of the system controller 55.The AO enable signal causes the system controller 55 to deliver an AOflow signal 934 to the solenoid 392 to open the flow valve 206. Asdiscussed previously, with the flow valve 206 opened, aqueous oxygenflows from the atomizer chamber 62 through the capillary tube 246 andinto the mixing chamber 64 to be mixed with the blood.

Bubble Detector

As mentioned previously, the system 10 advantageously includes a bubbledetector 74 that interfaces with a bubble sensor 76 to monitor theoxygen-enriched blood in the return tube 50 for bubbles. An exemplaryembodiment of the bubble detector 74 is illustrated in FIG. 51. Thebubble detector 74 includes a digital signal processor (DSP) 1000 thatoperates under software control to perform many of the functions of thebubble detector 74. The bubble detector 74 receives a return pressuresignal and a flow rate signal from the interlock system 44 on lines 1002and 1004, respectively. An analog-to-digital converter (ADC) 1006receives these analog signals and converts them to digital signals.These digital signals are transmitted from the ADC 1006 to amicrocontroller 1008. The microcontroller 1008 also receives user inputfrom an RS-232 serial communications port 1010 from the host/userinterface 66, as well as an initiate signal on line 1012 from theinterlock system 44.

The DSP 1000 and the microcontroller 1008 interface with one another viainterface and control logic 1014. Based on inputs from the DSP 1000 andthe microcontroller 1008, the interface and control logic 1014 deliversa transducer driver signal on line 1016 to a transducer driver 1018. Inresponse, the transducer driver 1018 delivers a signal to the transducer76 via line 1020. As illustrated in FIG. 52, the transmitted signaldelivered by the transducer 76 includes bursts of high frequency pulses1023A and 1023B. Each pulse burst may include 20 pulses for instance at3.6 MHz, with 50 microseconds between bursts. A return signal from thetransducer 76 is received on the line 1022. The signal received from thetransducer 76 on line 1022 resembles the transmitted signal 1021, but itis shifted later in time and has a smaller amplitude. It typically takeslonger than one burst period for a bubble to pass by the transducer 76.Therefore, each bubble may be sampled each time a pulse is deliveredduring the burst period, e.g., in this example, each bubble may besampled 20 times as it travels past the transducer 76.

The strength of the received signal on the line 1022 relative to thetransmitted signal on the line 1020 provides information regarding thepresence of bubbles within the return tube 50. As illustrated in FIG.54, the bubble sensor 76 includes an ultrasonic transmitter 1040 and anultrasonic receiver 1042. The bubble sensor 76 is advantageouslydisposed on the outside of the return tube 50. Thus, the ultrasonicsignal from the transmitter 1040 is transmitted through the return tube50, as well as any fluid within the return tube 50, to the receiver1042. If the fluid in the return tube 50 contains no bubbles, theultrasonic signal propagates from the transmitter 1040 to the receiver1042 in a relatively efficient manner. Thus, the signal strength of thereturn signal delivered by the receiver 1042 on the line 1022 isrelatively strong. However, if the fluid within the return tube 50contains bubbles 1044, as illustrated in FIG. 55, the ultrasonic signalreceived by the receiver 1042 will be attenuated. The attenuatedtransmission of the ultrasonic signal across fluid containing bubblesresults from the fact that the bubbles 1044 tend to scatter theultrasonic signal so that less of the transmitted signal is ultimatelyreceived by the receiver 1042.

As illustrated by way of example in FIG. 53, the first peak 1027Adepicts a signal that was transmitted through fluid containing nobubbles, and the second peak 1027B depicts a signal that was transmittedthrough fluid containing bubbles. The relative weakness of the peak1027B is demonstrated by a reduction in the peak 1027B. The attenuationof peak 1027B is related to the diameter of the bubble passing throughthe bubble sensor 76 at the time the signal was transmitted.Specifically, the attenuation in the signal is related to the bubble'scross-sectional area and thus square of the diameter of the bubble, sothat the square root of the signal is directly proportional to thebubble diameter.

To facilitate processing of the return signal, it is delivered to asignal conditioner 1024. The signal conditioner 1024 amplifies andfilters the return signal. The signal conditioner 1024 then detects theamount of ultrasonic energy of the signal and transmits it to an analogto digital converter (ADC) 1026. A signal 1025 delivered to the ADC 1026is illustrated in FIG. 53. As can be seen from a study of the signal1025, each of the high frequency pulse trains 1023A and 1023B nowresembles a single peak 1027A and 1027B, respectively. The ADC 1026samples only the peaks 1027A and 1027B in the amplitude signal 1025. Inthis example, each peak 1027A and 1027B is approximately 6.6microseconds in width, and the ADC 1026 samples 128 peaks to establish128 data points.

The digitized output of the ADC 1026 is delivered to a buffer, such as afirst-in/first-out (FIFO) buffer 1030. The buffer 1030 stores thedigitized representations of 128 peaks and delivers them one by one tothe DSP 1000. The interface and control logic 1014 controls delivery ofthe signals from the buffer 1030 to the DSP 1000.

The DSP 1000 reads the data points for each of the digitized peaks andsums them together. The sum of the digitized peaks correlates to theamount of ultrasonic energy received. In this embodiment, the DSP 1000maintains a running average of the sum of the last 16,000 or more peaks.The current sum is subtracted from the average to provide a high passfilter which effectively removes any DC offset. The DSP 1000 alsoperforms a low pass filter operation by convolving the resulting signalthrough an FIR array. In this example, the FIR array is a 64 pointarray. The filtering is performed to ensure that the bubbles arediscriminated from the noise in the signals. The resulting signals ofdifferent sized bubbles is illustrated in FIG. 61.

Once the DSP 1000 determines the diameter of each bubble detected, itcalculates the volume of the bubble. However, it should be understoodthat the volume of the bubble delivered to the patient 38 is affected bythe pressure of the fluid within the return tube 50. Because thepressure of the fluid within the return tube 50 is typically higher,e.g., approximately two to three atmospheres, as compared to the bloodwithin the patient's vessels, e.g., approximately one atmosphere, aconversion is advantageously performed to determine the volume of thebubble once it reaches the patient 38. Since the pressure in the returntube 50 is delivered to the bubble detector 74 on the line 1002, andsince the pressure of the patient's blood can be assumed to be oneatmosphere using the ideal gas law, the volume of the bubble at thepatient equals V_(p)=(P_(s)·V_(s))P_(a), where V_(p) is the volume ofthe bubble at the patient 38, P_(s) is the pressure at the bubble sensor76, V_(s) is the volume of the bubble at the bubble sensor 76, and P_(a)is atmospheric pressure.

The DSP 1000 advantageously places bubbles of certain sizes inappropriate “bins” or categories. In other words, the DSP 1000 maymaintain different categories of bubble sizes. For example, thecategories may include sixteen bins of 75 micron diameter increments.The number of bubbles in each category may be transmitted to the display32 so that a user can monitor the number and size of bubbles beingproduced during the surgical procedure. The number and size of bubblesalso may be monitored by the bubble detector 74 or elsewhere within thesystem 10 to monitor the operation of the system 10.

The bubble detector 74 also may accumulate total volume of all bubblesdetected over time. If the accumulated volume exceeds a prescribed limitwithin a prescribed time, then operation of the system 10 may bealtered. For example, if the total volume of bubbles exceeds 10microliters in a 90 minute period, the bubble detector 74 may deliver a“request to stop” signal on a line 1050. In this embodiment, the requestto stop signal is received by the interlock system 44, so that theinterlock system 44 can shut down the system 10 as previously described.Since most patients typically resolve small volumes of gas over time,the running total may be decremented as the procedure progresses so thatthe predetermined limit which triggers shut down of the system 10 willnot be reached as rapidly. In addition, prior to reaching thepredetermined limit, the bubble detector 74 may provide an early warningof an impending shut down so that the system controller 55 can lower thepO₂, level of the blood in the return tube 50 to curtail bubbleproduction and, thus, avoid shutdown.

Bubble Detector Evaluation or Calibration

Individual ultrasonic probes may have varying degrees of resolution.Therefore, a limitation on the bubble detector's ability to detectbubbles may arise when the size and/or velocity of some bubbles arebeyond the resolution of the probe. Depending on the circumstances, itis possible that microbubbles (bubbles with diameters of about 50 μm toabout 1000 μm) and/or macrobubbles (bubbles with diameters greater than1000 μm) may escape detection. When bubbles escape detection, theaccuracy of the bubble detector may be compromised.

Thus, it may be desirable to utilize a system and method for evaluatingthe bubble detection capabilities of a bubble detector. The system andmethod of evaluation described below is capable of determining themicrobubble and macrobubble reolution of the bubble detector at aplurality of flow rates and material viscosities. Generally speaking,bubbles of a determinable size are introduced into a flow material. Thesize and quantity of bubbles introduced into the flow material aremeasured by the bubble detector under evaluation. Thereafter, the sizeand quantity of bubbles introduced into the flow material are determinedindependently.

An exemplary embodiment of a calibration and evaluation system 1105 forbubble detectors, such as the bubble detector 74, is illustrated in FIG.56. The system and method permits a practitioner to control the bubblesize, rate of bubble production, and the rate of flow of flow material.The system 1105 employs a containment vessel 1110 for storing a flowmaterial 1112. The vessel 1110 includes an inlet 1116 and outlet 1118 sothat the flow material 1112 travels generally in the direction of thearrow 1119. A pump 1120, such as a peristaltic pump, is utilized toinduce and maintain a desired flow rate. Advantageously, the pump 1120is capable of transmitting the flow material 1112 at a plurality of flowrates. Flow materials 1112 of varying viscosity may be utilized and mayinclude newtonian or non-newtonian fluids. Typically, the viscosity ofthe flow material 1112 used for evaluation is comparable with theviscosity of the material utilized in the operational environment, e.g.,blood mixed with gas-enriched physiologic fluid in this example.

The system 1105 employs a first conduit 1130, typically of predeterminedinternal diameter and predetermined length, having a proximal end 1132and distal end 1134, through which the flow material 1112 may be passedat various rates. The proximal end 1132 is coupled to the outlet 1118 toreceive the flow material 1112 from the vessel 1110. The distal end 1134is coupled to a connecting device 1140. The connecting device 1140, forexample a T-connector, is typically positioned along the longitudinalaxis of the first conduit 1130 and in fluid communication therewith topermit the continued unimpeded flow of the flow material 1112.

A bubble-forming device 1143 may be used to induce bubble formation inthe flow material 1112 through the introduction of a bubble-formingmaterial 1150. The bubble-forming material 1150 typically includes agas, such as air. The flow material 1112 may contain a surfactant, suchas sodium dodecyl sulfate (SDS), to promote bubble formation andretention.

As best illustrated in FIGS. 57 and 58, the bubble-forming device 1143in this example includes a bubble-forming capillary 1144, which istypically of predetermined internal diameter and predetermined length.The capillary 1144 has a proximal end 1146 and a distal end 1148. Theproximal end 1146 is attached by a bubble-forming lumen 1153 to abubble-pumping device 1155, such as a syringe. The bubble-pumping device1155 is typically capable of injecting the bubble-forming material 1150into the flow material 1112 at various injection rates. The distal end1148 of the capillary 1144 is slidably arranged to be located within theinterior of the connecting device 1140 incident to the flow material1112, thus resulting in the generation of bubbles within the flowmaterial 1112. In this example, the capillary 1144 is positionedperpendicular or nearly perpendicular to the longitudinal axis of thedirection of flow of the flow material 1112 so that the resultant shearforce of the flow generates bubbles of a uniform size at a constantrate.

Bubble size may be regulated by the internal diameter of the capillary1144 or by positioning the distal portion 1148 of the capillary 1144 atvarious positions within the material flow. Increasing the internaldiameter of capillary 1144 increases bubble size. Similarly, positioningthe distal portion 1148 of the capillary 1144 away from the longitudinalaxis of the flow material 1112 increases bubble size. The rate of bubbleformation may be varied by increasing or decreasing the flow rate of thebubble-forming material 1150 introduced into the flow material 1112. Forexample, an increase in the flow rate of the bubble-forming material1150 increases the rate of bubble formation in the flow material 1112.

The system 1105 further employs a second conduit 1170, which is,typically of predetermined internal diameter and predetermined length. Aproximal end 1172 of the second conduit 1170 is coupled to theconnecting device 1140, and a distal end 1174 of the second conduit 1170is coupled to the inlet 1116 of the containment vessel 1110. To maintaina substantially constant flow rate in the conduits 1130 and 1170, thesecond conduit 1170 is usually coaxially aligned with the first conduit1130, and the diameter of the second conduit 1170 is usually equivalentto the diameter of the first conduit 1130. The probe 76 of the bubbledetector 74 to be evaluated is positioned proximal to the second conduit1170 to enable detection of bubbles within the flow material 1112passing through the second conduit 1170.

The connecting device 1140 may be optically transparent to permit visualinspection of the bubble generation process. Indeed, a recording device1160, such as a CCD camera, may be focused on the distal end 1148 of thecapillary 1144 to observe and record the size and quantity of bubbleswithin the flow material 1112. Thus, bubble detectors, such as thebubble detector 74 for example, may be calibrated by comparing the sizeand quantity of bubbles detected by the probe 76 with the size andquantity of the bubbles measured by the recording device 1160. A secondexamining device (not shown) may be positioned along second conduit 1170between the bubble detector probe 76 and the inlet 1116 of thecontainment vessel 1110 to provide the practitioner access to the flowmaterial 1112.

In operation, flow is initiated by activating the pump 1120. The flowrate of the flow material 1112 is permitted to stabilize beforeintroducing bubbles to the system 1105. Once the system 1105 hasstabilized, bubbles are introduced to the flow material 1112 byactivating the bubble-forming device 1143. The system 1105 is permittedto stabilize once again before calibrating the bubble detector 74.

The microbubble resolution of the bubble detector 74 may be determinedby introducing bubbles of successively smaller diameters in successivetests. The macrobubble resolution of the bubble detector 74 may bedetermined in a similar manner by introducing bubbles of successivelylarger diameters in successive tests. Once the rate of bubble generationand flow rate have stabilized, the recording device 1160 is activated torecord the rate of bubble generation and the size of the bubblesgenerated. The bubble detector 74 to be evaluated is activated for apredetermined amount of time.

The probe 76 examines the bubbles which are generally of known size andquantity, and the probe 76 delivers corresponding signals to the bubbledetector 74. The size and quantity of bubbles recorded by the bubbledetector 74 are compared to the size and quantity of the bubblesrecorded by the recording device 1160. Typically, such comparison isperformed at a plurality of signal strengths and bubble sizes.Thereafter, one skilled in the art of mathematics may graphicallyrepresent this relationship and extrapolate the projected signalstrengths at a plurality of bubble sizes. When the signal-to-bubble sizerelation is graphically plotted, one skilled in the art of mathematicscan calculate one or more calibration constants based on the fit of thesignal strength to bubble size relationship. The calibration constant(s)can be programmed into the bubble detector 74 to calibrate the bubbledetector 74.

An alternative embodiment of the calibration and evaluation system 1105is identical to the previously described system except for theincorporation of a pulse dampener 1180, as illustrated in FIG. 59. Thepulse dampener 1180 reduces or eliminates pressure oscillations producedby the pump 1120. In addition, relatively large bubbles that may berecirculated within the flow circuit become trapped within the pulsedampener 1180 so that they do not disturb the controlled formation ofbubbles by the bubble-forming device 1143.

As shown with further reference to FIG. 60, the pulse dampener 1180comprises a vessel body 1181 having an inlet 1182 and an outlet 1184.The inlet 1182 is coupled in the first conduit 1130 between the pump1120 and the connecting device 1140. The pump 1120 forces the flowmaterial 1112 into the vessel body 1181 through the inlet 1182. Thepressure exerted by the pump 1120 is maintained within the vessel body1181, thus forcing the flow material 1112 through the outlet 1184. Thus,any bubbles produced by the pump 1120 are trapped prior to reaching theconnecting device 1140.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

1. A method of enriching a bodily fluid with a gas, the methodcomprising the acts of: (a) delivering a physiologic fluid underpressure from a fluid supply chamber of a housing to an atomizerdisposed in an atomizing chamber of the housing; (b) atomizing thephysiologic fluid using the atomizer and delivering droplets of theatomized physiologic fluid into a pressurized gas within the atomizingchamber to form a gas-enriched physiologic fluid; (c) delivering thegas-enriched physiologic fluid from the atomizing chamber into apressurized mixing chamber of the housing by using the pressurized gaswithin the atomizing chamber; and (d) delivering a bodily fluid to thepressurized mixing chamber to mix with the gas-enriched physiologicfluid to form a gas-enriched bodily fluid, wherein said fluid supplychamber, atomizing chamber, and mixing chamber are housed within thesame housing.
 2. The method, as set forth in claim 1, wherein act (a)comprises the act of: pumping the physiologic fluid through a fluidoutlet in the fluid supply chamber.
 3. The method, as set forth in claim1, wherein act (b) comprises the act of: routing the physiologic fluidthrough a fluid inlet of the atomizing chamber when a fill valve beingcoupled to the fluid inlet of the atomizing chamber is open.
 4. Themethod, as set forth in claim 1, wherein act (c) comprises the act of:routing the gas-enriched physiologic fluid through a fluid outlet of theatomizing chamber when a flow valve being coupled to the fluid outlet ofthe atomizing chamber is open.
 5. The method, as set forth in claim 1,wherein act (d) comprises the act of: delivering the gas-enrichedphysiologic fluid to the mixing chamber using a fluid delivery devicedisposed in the mixing chamber.
 6. The method according to claim 1,wherein the pressure in the pressurized atomizing chamber is greaterthan 200 psi.
 7. The method according to claim 1, wherein the pressurein the pressurized atomizing chamber is greater than 600 psi.